This isn't a Microsoft product.

Yes at least some of the people. Their instructions for getting a new SQL 2017 Docker image (somewhere not sure if it was the official documentation or Microsoft hosted blogs that should know better) included apt get update on the Linux container after download.

I was bit surprised so much is out of date for the official container.

But I mean... I’m new to docker and this was my first introduction... but I’m pretty sure from what I’ve read that it’s a huge no no.

The author of this Dockerfile didn't publish it with any affiliation with Microsoft.